issues on Heat exchanger in simscape 2P-TL and Two-Phase Fluid Properties

I have a System-Level Condenser Evaporator (2P-TL) with ISOBUTANE on the hot side and AIR on the cold side.

The air on the cold side has a temperature of 210K~315K, enthalpy of 196~309kJ/kg, and a mass flow rate of 540kg/s.

On the hot side, I set the temperature of isobutane to 320K~215K with enthalpy 622~77kJ/kg at first, but isobutane will phase change at around 310K, so I changed the temperature to 300K~215K with enthalpy 162~77kJ/kg to make sure that the mass is in the liquid state and won't phase change to a gas.

Since I changed the temperature from 320K to 300K, my model doesn't work and shows an error:

Failed to determine size of heat exchanger from the specified nominal operating condition. Try reducing Nominal rate of heat transfer or increasing Nominal mass flow rate.

I changed the heat exchanger from 2P-TL to 2P-2P and it doesn't solve the problem, both heat exchangers can run at 320K but 300K reports an error.

I can't find the problem and am not quite sure if there will be any other problems if I continue to run the model with 320K?

[Yifeng Tang]

The error message is saying that the nominal condition you've provided is physically impossible. This occurs usually when the nominal heat flow will resulting in the outlet temperature of the hot side being colder than the inlet temperature of the cold side, in violation of the 2nd law of thermal dynamics.

When you say that "the air on the cold side has a temperature of 210K~315K", do you mean its temperature is expected to rise from 210K to 315K? If so, it is unreasonable to change your butane inlet temperature to 300K, as it's IMPOSSIBLE to heat the air to 315K with 300K butane on the other side. The phase change temperature of Butane depends on its pressure. If you don't expect or don't want the phase change to occur, maybe check whether the pressure is correctly set.